show your colours
show (one's) (true) colours
To reveal what one truly believes, thinks, or wants; to act in accordance with one's real personality, character, or disposition. Primarily heard in UK. Dave said all along that he only wanted this deal because it was in the company's best interest, but he showed his true colours once he realised that he wouldn't get any special commission for his efforts. It's only in times of crisis that your friends will really show their colours.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
show your (true) coloursreveal your real character or intentions, especially when these are disreputable or dishonourable.
Farlex Partner Idioms Dictionary © Farlex 2017